Production of vulcanizable rubber-containing mixtures



United States Patent 01 fice 3,520,954 Patented July 21, 1970 3,520,954 PRODUCTION OF VULCANIZABLE RUBBER- CONTAINING MIXTURES Harald Blumel and Wilhelm Schanzer, Marl, Germany,

assignors to Chemische Werke Huls A.G., Marl, Germany No Drawing. Continuation of application Ser. No. 457,815, May 21, 1965. This application Jan. 29, 1968, Ser. No. 701,469 Claims priority, application Germany, May 22, 1964, 1,261,311 Int. Cl. C08d 9/04, 13/02, N09

US. Cl. 260894 7 Claims ABSTRACT OF THE DISCLOSURE Vulcanized products of cold rubber and polybutadiene, such products having improved resistance to crack growth by virtue of the cold rubber and polybutadiene being blended as latices before being compounded and vulcanized.

This application is a continuation of application, Ser. No. 457,815, filed May 21, 1965, now abandoned.

The present invention relates to rubber compositions based on polybutadiene and cold rubber.

It has been known to utilize for the production of rubber articles, particularly those which are subjected to variable and repeated dynamic stresses, blends or mixtures of different rubber types.

Thus, polybutadiene rubber produced according to the Ziegler Process has already been blended with natural rubber or cold rubber; in this process, it is possible to partially combine the advantageous abrasion properties of the polybutadiene rubber with the excellent processing properties of natural rubber or cold rubber. Also, when using vulcanizable blends of solid polybutadiene rubber manufactured according to an emulsion polymerization process, and solid cold rubber as conventionally produced, the advantages of an increased wear resistance in comparison with pure cold rubber mixtures (particularly important for the tire treads), are combined with the advantage of practically the same case of processing of straight cold rubber. These previously known blends were produced in all cases during the production of the vulcanizable rubber recipes in conventional blending devices, for example rubber mills or internal mixers. In such devices the dry rubbers are mixed together, inasmuch as it is then possible in what amounts to one mixing step, to add simultaneously or immediately afterward further conventional ingredients of the rubber mixture, for example fillers, metallic oxides, softeners, agents which impart resistance to aging, vulcanizing agents, etc. The vulcanized products produced by this method exhibit good properties, by and large, but their resistance to the growth of cracks upon repeated flex is relatively low.

An object of this invention is to provide an improvement in the production of such rubber blends whereby the final vulcanized products exhibit much better resistance to the growth of cracks upon being subjected to repeated flexes.

Another object is to provide vulcanized products as produced by the process of this invention.

Still another object is to provide combined latexes, as produced according to this invention.

Upon further study of the specification and claims, other objects and advantages of the present invention will become apparent.

To attain the objects of this invention, there is provided a process based on the discovery that it is possible to produce vulcanizable rubber-containing mixtures leading to vulcanized products with improved resistance to the growth of cracks, if as the rubber component of this mixture rubber blends are used which are obtained by combining the aqueous latices of polybutadiene rubber produced according to an emulsion polymerization process, on the one hand, and of cold rubber on the other hand, and by conventionally working up these latices.

Polybutadiene rubbers which are produced according to an emulsion polymerization process are to be understood to mean those polybutadiene rubbers which are produced at low temperatures with hydroperoxidecatalysts, i.e. at temperatures below 20 C., preferably at 5 C. For more specific information regarding the production of such emulsions, attention is invited to the pertinent patents and chemical literature, eg the Deutsche Auslegeschrift 1,024,242 (U.S. Rubber Company, N.Y.), Example 9.

Cold rubbers which are suitable are, for example, emulsion copolymers of butadiene and styrene, or butadiene and acrylonitrile, which are produced at temperatures below 20 C., preferably at 5 C. For more specific information regarding the production of these cold rubbers, attention is invited to the pertinent patents and chemical literature, e.g. the Deutsche Auslegeschrift 1,024,242 (US. Rubber Company, N.Y.), Examples 1 to 8.

In general, the weight ratio of the components of the blend can be varied in all proportions, preferably from :5 to 10:90, more preferably in the range of 75:25 to 25:75. The weight ratios refer to solid matter.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

EXAMPLE 1 A polybutadiene rubber latex produced by emulsion polymerization at 5 C. is mixed, under stirring, with a cold rubber latex (rubber Type 1500) in accordance with the data contained in Table 1 infra.

1 Of rubbery solid matter, produced according to Example 9 of Deutsche Auslegeschriit 1,024,242 (US. Rubber Company).

2 0f rubbery solid matter, rubber Type 1500 refer to Description of Types of Styrene Butadiene Rubber (SB R) and Butadiene Rubber (B R) Dry Polymers and Latices, International Institute of Synthetic Rubber Producers, Inc., August 1963 Edition, Table II, Gold Non-Pigmented Polymers, line 1.

The latex mixtures are mixed with 1.25 percent by weight, based on rubber, of phenyl-flmaphthylamine as a stabilizer and coagulated, in a conventional manner, with aqueous NaCl solution and sulfuric acid. The rubber blends precipitate in the form of coarse granules which are washed, ground, and dried in the usual way.

With the thus-produced rubber blends, the correspondingfinished mixtures are produced, according to the recipe set forth in Table 2. This is done in a Werner und Pfleiderer masticator of the GK 2 Type, at 40 rpm. for the front rotor, at a jacket temperature of 50 C., and at a total mixing time of 12 minutes. The basic mixtures free of vulcanizing agents are obtained thereby, and after a storage time of 12 hours, the corresponding finished mixtures are produced on the roll mill by admixture of sulfur and accelerator. The values for the vulcanized product obtained by a vulcanization at C. are shown in Table 3. The mixtures are designated with II, III, and IV, depending upon the specific rubber blend set forth in Table 1. For purposes of comparison, in addition to these mixtures, there are also described those mixtures which are obtained with the rubber components on which the rubber blends are based (mixtures I and V, respectively) In parallel with the above, mixtures are produced containing blends of polybutadiene rubber, produced according to an emulsion polymerization process, and cold rubber in the same blend proportions as mixtures II, III, and IV; however, there is the difference that the rubber TABLE Q (IN PARTS BY blend components used for this purpose are blended and mixed in a conventional manner in the form of dry I II III IV v rubbers. These mixtures are designated, corresponding to P1Ybutadim rubber (Produced their blend proportions, as IIa, 111a, and IVa.

according to an emulsion-polym- 1O I d erization process) 100.00 75.00 50.00 25.00 From Tables 3 and 4, it can be seen that the b en s 551 351 152 Type 150 500 288 2'88 288 2-88 produced in accordance with the invention lead to A Carbon black 47-50 4 47- 50 4 4 5 markedly improved values for resistance to the growth Aromatic plasticizer 8.00 8.00 8.00 8.00 8.00 Phenyl-fl-naphthyla ine 0 1,00 00 1,00 00 of cracks of the vulcanized products produced therefrom, 32 512 O0 1 O0 100 100 1 00 in comparison with the blends produced according to Protectivewax for sunlight resist 1 00 1 0O 1 00 1 00 1 0 the state Of the art.

8 Sriiiiir 1.50 1.50 1.50 1.50 1.50 EXAMPLE 2 N -cyclohexyl-2-benzothiazyl suliene amide .75 0.75 0.75 0.75 0.75

A polybutadiene rubber latex produced by emulslon 2 13233385? polymerization at 5 C. is mixed, under stirring, with gggf llf yig fig f ffg fi gg ig g gfi figgs a h an oil-containing cold rubber latex (rubber Type 1709) C-atorns: 10%. in correspondence with the data contained in the follow- 0c0ke11te. g Table 5- TABLE 3 Perma- Resistance 2 to nent Tear Elasticity crack growth Type of Mooney Elongaelongaresistance Hard- DVM, upon flex- Mixture Defo viscosity Vulcan- Tensile tion Modulus tron (kg.absoncss 22 C. 75 C. ab raing inaDe- (See plasticolmixture izing time strength (per- 300% (persolute t0 (degrees perpersion Mattla Table 1) ity ML-4 (150 C.) (kg./cm. cent) (kg/0111. cent) Iohlc Shore) cent cent (mmfl) machine 15' 122 475 54 11 11 5s 45 44 51 I 1950/ 70 30' 171 415 105 Broken 13 01 4s 52 53 9,500. 60' 172 385 110 Broken 11 01 50 53 12,200

12 2?; it it; it it 51 15" 0' 173 535 73 20 15 5s 45 31200 H 1650/30 59 i 20' 181 450 100 s 14 60 4s 52 221700 2G 62 5 r 12 2: 2: 5. 30' 173 470 55 12 7 m 1375/27 54 50' 102 455 91 0 14 50 45 53 351000 120' 193 480 s 13 e0 46 52 e 12 r .1 a 12 22 a; .5 30' 545 50 5 W 53 00' 218 545 85 10 17 e0 45 52 351000 15' 45 550 12 8 5; 5 4 5 4 1 3 c 7 {3. 3 15111 1. at 30' 227 030 74 8 5 3 3 0 0. V 1025/20 53 60' 235 550 05 10 15 00 43 55 00,000.

1 As per DIN 53-516 (German Industry Norm 53-516). 2 Number of strokes to widen a 2 mm. crack to 20 mm.

3 As per DIN 53-514.

4 As per DIN 53-522.

abrasion resistance.

' In this case a crack width of only 18.3 mm. is reached at a stroke number of 115,000 in all other cases the crack width being 20 1n1n.1or the given stroke numbers.

TABLE 4 Perma Resistance 2 to nent Tear Elasticity crack growth Type of Mooney Elongaelongaresistance Hard- M, 1 upon flex- Mixture Defo viscosity Vulcan- Tensile tion Modulus tion (kg. absoness 22 C. 75 0. abraing in a De- (See plasticof mixture izing time strength (per- 300% (persolute to (degrees perpersion Mattia Table 1) ity 3 ML-4 C.) (kg/cm. cent) (kg/cm. cent) Pohle Shore) cent. cent. (mm. machine 0 17 97 7 6 6 5 Ha 1550/34 62 50' 415 110 Broken 12 01 48 120 188 435 100 7 12 61 48 r r 3 1: 12

0 16 520 9 1 1 ma 1350/29 56 50' 187 440 103 Broken 13 50 47 120 221 495 103 9 14 60 47 21,5: 2922) 745 23 3g 10 20 0 1 545 81 1 18 9 Na 1200/24 54 00' 180 440 101 Broken 15 00 45 120' 240 535 9 1 14 60 45 1 As per DIN 53-516 (German Industry Norm 53-516), abrasion resistance.

1 Of rubbery solid matter, produced according to Examples 1 to 8 of Deutsche Auslegeschrift 1,024,242 (U.S. Rubber Company).

2 Of rubbery solid matter, rubber Type 1709, refer to Description of Types of Styrene Butadiene Rubber (SBR) and Butadlene Rubber (B R) Dry Polymers and Latices, International Institute of Synthetic Rubbelr Producers, Inc., August 1963 Edition, Table II, Gold 011 Masterbatch, ine 11.

The latex mixtures are mixed with 1.25 percent by weight, based on rubber, of phenyl-fl-naphthylamine as tures VI, VIII, and VII; there is, however, the difference that the rubber blend components used therefor are blended and mixed with one another in the form of dry rubbers during the production of the mixture, in accordance with the state of the art. These mixtures are designated as Vla, W111, and W110, corresponding to the blend proportions.

In the same manner as in Example 1, there can be seen from Tables 7 and 8 that the blends produced in accordance with the present invention exhibit markedly improved values for the resistance to the growth of cracks upon repeated flex of the vulcanized products manufactured therefrom, in comparison to the blends obtained according to the prior art.

TABLE 6.-MIXTURE COMPOSITION (IN PARTS BY WEIGHT) I VI VII VIII IX a stabihzer, and coagulated in a conventional manner with aqueous NaCl solution and sulfuric acid. The rubber gg f g g ggf ggg fi blends precipitate in the form of large granules which 20 erization process) 100.00 75.00 50.00 25.00 are Washed, ground, and dried in a known manner. Here, g gg Type 1709 b 2- 88 g-gg 2-88 88 too, there are produced, in accordance with the recipe IIAF Ca1-bon 1515515.. .III 47.50 47.50 47: 50 47.50 47150 set forth in Table 6 and analogous to Example 1, vulgi g f j fg giffil% figg 5 88 gg -88 -88 8g canizable rubber mixtures which are designated as VI, N-phenyl-N-isopropyl-phenylene VII, and VIII, according to the rubber blend proportion 25 g f gi- 5,;" 1:'g 0O 1 O0 of Table 6. For reasons of comparison, there are desistauce 1. 00 1.00 1. 90 1. 00 1. 00 scribed, in addition to these mixtures, those which were i g h'i }ij ibgiifiiigdmff 1 produced with the rubber components on which the rubamide 0.90 0.90 0 90 0.90 0.90

ber blends are based (mixtures I and IX, respectively). Refer to Table In parallel with the above, mixtures are produced 30 z g l Tag R 5 f n l d t A b d ap 0 en avmg O O\V1I'I ana y 3. BS2 roma 10 01111 Whlch P blends ofpolybutadlene rubber, Produced C-atoms, 44%; Naphthtenic bound? Caton1s, 37%; Paraliinic bound; by an emulsion polymerization process, and cold rubber g g i. extended with oil, in the same blend proportions as mix- CO TABLE 7 Perrna- Resistance 2 T f M El 1 nent LTear H d Elasticity DVNI to crack grogth ype o ooney ongae ongaresls 'ance ar u on ex- Mixture Defo viscosity Vulcan- Tensile tion Modulus tion (kg. absoness 22 C. 75 C. zibraing inaDe- (See plasticof mixture izing time strength (per- 300% (perlute to (degrees perpersion Mattie Table 1) ity 3 ML-4 (150 C.) (kg/en cent) (kg/cm. cent) Iohle Shore) cent cent (mm. machine 4 15' 116 650 38 19 11 52 41 VI 1400/34 53 30' 192 475 9 12 60 47 60' 181 400 119 7 10 61 48 129' 175 395 116 7 10 61 48 15' 85 785 20 33 9 46 38 VII 1200/32 47 30' 188 495 88 11 12 59 45 60 179 420 107 8 10 60 54 120 186 435 8 8 60 44 15 138 880 23 31 12 46 36 VIII 1000/30 40 30' 202 565 77 17 12 55 40 60 194 500 91 12 11 56 40 206 515 94 12 11 56 40 15 19 1035 3 100 2 35 33 IX 825/25 38 30' 191 605 68 19 13 51 35 60 190 515 86 14 10 55 35 120' 196 530 86 12 11 55 35 1 As per DIN 53-516 (German Industry Nonn 53-516), abrasion resistance. 2 Number of strokes to widen a 2 mm. crack to 20 mm. 3 As per DIN 53-514. 4 As per DIN 53-522.

TABLE 8 Perma- Resistance 2 T f M El 1ncnt; tTear H d Elasticity DVVI to crack grogivth ype 0 OOIIGY ongae Ol gfl- I'CSIS 8 1166 ar 4 11 011 EX- Mixture Defo viscosity Vulcan- Tensile tion Modulus tion (kg.absoness 22 C. 75C. abraing inaDe- (See plasticof mixture izing time strength (per- 300% (perlute to (degrees pcrpersion Mattia Table 1) ity ML-4 C.) (kg./cm. cent) (kg./cm. cent) Pohle Shore) cent. cent. (mmfi) n1achine 15' 188 555 73 11 14 59 45 59 VIa 1400/36 55 30' 172 390 115 7 11 61 48 59 60' 380 124 6 9 62 48 58 120' 184 395 122 7 9 61 48 57 v 15' 137 745 33 22 12 50 39 45 VIIa 1250/33 49 30' 191 470 96 19 12 60 45 58 15' 77 855 15 38 8 45 37 40 VIIIa-... 1050/30 43 30' 188 520 79 12 13 55 42 57 1 As per DIN 53-516 (German Industry Norm 53-516), abrasion resistance.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

What is claimed is:

1. A vulcanized rubbery product of polybutadiene and butadiene-styrene cold rubber, said product having substantially improved resistance to the growth of cracks upon being subjected to repeated flexing, and being produced by the process comprising the steps of (a) blending an emulsion-polybutadiene and a cold rubber consisting essentially of a butadiene-styrene copolymer, said blending step comprising producing said cold rubber in the form of an aqueous latex thereof; producing said emulsion-polybutadiene in the form of an aqueous latex thereof; combining the two latices to obtain a substantially homogeneous latex of the two rubbery polymers, and separating the solids of the combined latices;

(b) masticating and compounding the resultant solids into a mixture suitable for vulcanization; and

(c) vulcanizing the resultant mixture; said rubbery product having an improved resistance to the growth of cracks as compared to the products of the same composition wherein step (a) is a mechanical blending step.

2. The product of claim 1 wherein the polybutadiene is polymerized at a temperature of about 5 C.

3. The product of claim 1 wherein the cold rubber is polymerized at a temperature of about 5 C.

4. The product of claim 1 wherein the weight ratio of cold rubber to polybutadiene is 90:10 to 10:90.

5. The product of claim 1 Wherein the weight ratio of cold rubber to polybutadiene is 75:25 to 25:75.

6. A vulcanized product as defined by claim 1 wherein said product is a tire tread.

7. A vulcanized product as defined by claim 3 wherein said product is a tire tread.

References Cited UNITED STATES PATENTS 2,657,190 10/1953 Banes et al. 260894 FOREIGN PATENTS 666,753 7/ 1963 Canada.

SAMUEL H. MLEOH, Primary Examiner W. J. BRIGGS, JR., Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.520, 954 lU-LW 9 Inventor(s) HARAID BLUm 61; a1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Table 3, 111, under Column "Elongation (percent)" 10th number down, change "470" to ---57Q--- Column 3, Table 3, I, under Column "Modulus 300%, "4th number down, change "121" to ---1l2--- Column 6, Table 7, VII, under Column "Elasticity, 22 C.

percent" 11th number down, change "54" to ---45-- SIGNED m1 SEALED 00mm Edwmlllfletchnnlr. mmn, .m.

Officer M8810? 0: Pat! FORM PC2-1050 (10-69) USCOMM-DC 60376-P69 1 ll 5 GOVERNMENT PRINTING OFFICK. III! O-ICG-SSI 

